Referring to FIGS. 1 and 2, a prior art surgical instrument is shown that is used to resect tissue using a tube-in-tube construction that shears tissue disposed between cutting edges of an outer non-rotating tube 370 and an inner rotating shaft 374 of a rotary cutter 300, as more fully explained in U.S. Pat. No. 5,871,493, which is incorporated herein by reference in its entirety. Outer tube 370 is connected to a hub 320 at a proximal region 371 of outer tube 370, and inner shaft 374 is rotatably received in hub 320 and outer tube 370. Inner shaft 374 includes a tube 376 located within outer tube 370. Tube 376 defines an aspiration lumen 378 and connects to a motor coupling 350 located in a proximal region of shaft 374 and partially received within hub 320. Motor coupling 350 includes an extension 355 coupled to a drive mechanism 115 that rotates shaft 374 relative to hub 320 and outer tube 370. Hub 320 includes a coupling in the form of a resilient latching mechanism 310 for connecting rotary cutter 300 to a handpiece 100, as discussed in U.S. Pat. No. 5,871,493. In particular, mechanism 310 includes a cantilevered resilient arm 315 with ramped latches 330 that engage an annular flange 610 in handpiece 100 to axially secure rotary cutter 300 to handpiece 100 as shown in FIG. 7B of U.S. Pat. No. 5,871,493. Other embodiments of the latching mechanism are also described in U.S. Pat. No. 5,871,493.
Handpiece 100 (FIG. 2) includes an aspiration channel 630 terminating at an aspiration opening 633 for applying suction to aspiration lumen 378 to remove fluid and cut tissue from a surgical site. Aspiration lumen 378 in tube 376 of shaft 374 has a proximal opening 375 that communicates with a through hole 380 in motor coupling 350. Suction is applied through aspiration channel 630 to draw material through a side-facing window 305 in outer tube 370 and a side-facing window 307 in inner tube 376, into lumen 378, and through lumen opening 375 and both ends of hole 380 to aspiration channel 630.